The present invention relates to a universal joint, and more particularly to a universal joint for use with drive spindles of the type which are subjected to high load.
With drive spindles including a universal joint and incorporated in heavy-duty mechanical apparatus such as rolling mills, the trunnion neck portion of the yoke pin included in the universal joint is structurally the weakest portion of the spindle and is therefore prone to fracture when subjected to dynamic load and even when subjected to static load. Accordingly, trunnions of universal joints heretofore used are designed to have the largest possible diameter so as to minimize the bending stress of the trunnion neck portion relative to the torque acting on the bearing.
FIG. 1 shows a universal joint in which the diameter d of a trunnion 1 is made as large as possible. Since the swing diameter D of the universal joint is limited, the joint is so designed that the working angle of the joint is minimized for example to 5.degree. to 10.degree., with the smallest possible clearance S formed between the circumferentially adjacent bearing cases 2 in order to give the trunnion 1 an increased diameter. However, the limitation on the working angle of the universal joint is restricted; the set of components including the trunnion 1, bearing case 2, needle-like rollers 3 and unillustrated fastening bolts must be confined to a space within an angular range of 90.degree. about the center. The space thus limited imposes a restriction on the diameter of the trunnion 1 and therefore on the increase of the strength of the trunnion neck portion. Thus, it is impossible to obtain the desired strength, making it extremely difficult to increase the torque capacity of the drive spindle.